Immediate hypersensitivity reactions following monovalent 2009 pandemic influenza A (H1N1) vaccines: reports to VAERS.

•The rate of reported hypersensitivity reactions following 2009 H1N1 vaccine was 10.8 per million.•The rates of hypersensitivity reactions were equal for 3 manufacturers of vaccine, but higher following live vaccine.•Females of childbearing age had higher rates of allergic reactions than males, but equal rates in other ages.•Epinephrine was underutilized for treatment of anaphylaxis following influenza vaccination.